共查询到20条相似文献，搜索用时 15 毫秒
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We investigate the problem of transition from galactic cosmic rays to extragalactic ultra-high energy cosmic rays. Using the model for extragalactic ultra-high energy cosmic rays and observed all-particle cosmic ray spectrum, we calculate the galactic spectrum of iron nuclei in the energy range 108–109 GeV. The flux and spectrum predicted at lower energies agree well with the KASCADE data. The transition from galactic to extragalactic cosmic rays is distinctly seen in spectra of protons and iron nuclei, when they are measured separately. The shape of the predicted iron spectrum agrees with the Hall diffusion. 相似文献
3.
J. R. Wayland 《Astrophysics and Space Science》1972,18(1):89-93
The possibility that a series of explosions of the galactic nuclei every 5×106 yr can cause a substantial flux of cosmic ray particles at the vicinity of the Earth is investigated. The steady flux of cosmic radiation forces the conclusion that there have been explosions back to 109 yr if this is a dominant source of cosmic rays. 相似文献
4.
E. N. Parker 《Astrophysics and Space Science》1973,24(1):279-288
The origin and behavior of cosmic rays in the Galaxy depends crucially upon whether the galactic magnetic field has a closed topology, as does the field of Earth, or whether a major fraction of the lines of force connect into extragalactic space. If the latter, then cosmic rays could be of extragalactic origin, or they could be of galactic origin, detained in the Galaxy by the scattering offered by hydromagnetic waves, etc. If, on the other hand, the field is largely closed, then cosmic rays cannot be of extragalactic origin (at least below 1016 eV). They must be of galactic origin and escape because their collective pressure inflates the galactic field and they push their way out.This paper examines the structure of a galactic field that opens initially into intergalactic space and, with the inclusion of turbulent diffusion, finds no possibility for maintaining a significant magnetic connection with an extragalactic field. Unless some mechanism can be found, we are forced to the conclusion that the field is closed, that cosmic rays are of galactic origin, and that cosmic rays escape from the Galaxy only by pushing their way out. 相似文献
5.
Yu. L. Kolesnyk A. I. Klyuyeva B. A. Shakhov Yu. I. Fedorov 《Kinematics and Physics of Celestial Bodies》2016,32(6):265-275
The effect of high-speed recurrent solar wind streams from coronal holes on the galactic cosmic rays intensity is investigated. The distribution of galactic cosmic rays for different solar cycles is considered based on the data of the world network of neutron monitors. Within the inhomogeneous model, which includes a homogeneous background and regions of high-speed streams (HSS’s), the transport equation has been solved and the effect of HSS’s on the spatial distribution of galactic cosmic rays is estimated. It is shown that theoretical calculations are agreed with the experimental results obtained for 2000–2014 under different assumptions about the mean free path of cosmic rays in the corresponding period of HSS’s. 相似文献
6.
W. Tkaczyk 《Astrophysics and Space Science》1997,258(1-2):251-267
7.
Cosmic rays are a sample of solar, galactic and extragalactic matter. Their origin and properties are one of the most intriguing question in modern astrophysics. The most energetic events and active objects in the Universe: supernovae explosion, pulsars, relativistic jets, active galactic nuclei, have been proposed as sources of cosmic rays although unambiguous evidences have still to be found. Electrons, while comprising ∼1% of the cosmic radiation, have unique features providing important information regarding the origin and propagation of cosmic rays in the Galaxy that is not accessible from the study of the cosmic-ray nuclear components due to their differing energy-loss processes. In this paper we will analyse, discussing the experimental uncertainties and challenges, the most recent measurements on cosmic-ray nuclei and, in particular, electrons with energies from tens of GeV into the TeV region. 相似文献
8.
Mingzhe Zhai 《Meteoritics & planetary science》1995,30(6):733-737
Abstract— The new B solar-system abundance calculated by Zhai and Shaw (1994), 16.9 atoms/106 Si (or 606 atoms/1012 H) is used to reevaluate the different possibilities of LiBeB (except 7Li) nucleosynthesis. The revised abundances support two models: (1) Light elements were formed by continual bombardment of interstellar medium (ISM) by galactic cosmic rays (GCRs), but these galactic cosmic rays should contain a very intense low-energy component, in the form of E?5 which cannot be observed near the Earth due to solar modulation effects; (2) Light elements are a mixture of two sources. In the first source, light elements were synthesized by continual bombardment of interstellar medium by galactic cosmic rays. In the second source, they were made by the interactions of C and O nuclei ejected from supernovae with the H and He in the surrounding gas. The first source constitutes ～46% of total B. The Si-normalized and CI-meteorite-normalized abundances of common and volatile elements in carbonaceous chondrites show a linear correlation with their condensation temperatures. Using this relationship and the normalized B abundances in CM, CO, and CV meteorites, we can estimate the B condensation temperature to be ～910 K, which is similar to Ga. 相似文献
9.
A. V. Uryson 《Astronomy Letters》2018,44(8-9):541-545
The extragalactic sources of ultra-high-energy (E > 4 × 1019 eV) cosmic rays that make a small contribution to the flux of particles recorded by ground-based arrays are discussed. We show that cosmic rays from such sources can produce a noticeable diffuse gamma-ray flux in intergalactic space compared to the the data obtained with Fermi LAT (onboard the Fermi space observatory). A possible type of active galactic nuclei (AGNs) in which cosmi-ray protons can be accelerated to energies 1021 eV is considered as an illustration of such sources. We conclude that ultra-high-energy cosmic rays from the AGNs being discussed can contribute significantly to the extragalactic diffuse gamma-ray emission. In addition, a constraint on the fraction of the AGNs under consideration relative to the BL Lac objects and radio galaxies has been obtained from a comparison with the Fermi LAT data. 相似文献
10.
T. N. Rengarajan 《Astrophysics and Space Science》1975,32(1):55-75
The capabilities and limitations of pulsars as sources of cosmic rays are reviewed in the light of experimental observations. Pulsars can supply the cosmic ray power if they have rotational velocities in excess of 700 rad s?1 at birth. Though this is theoretically possible, there is no experimental proof for the same. Pulsars can accelerate particles to the highest energies of 1020 eV, but in general, the spectra on simple considerations, turn out to be flatter than the observed cosmic ray spectrum. At the highest energies, absorption processes due to fragmentation and photodisintegration dominate for heavy nuclei. The existence of a steady flux of cosmic rays of energy greater than 1017 eV demands acceleration of particles to last over fifty years, the time interval between supernovae outbursts, whereas the expected period of activity is less than a few years. Finally, the problem of anisotropy with relevance to pulsars as sources and the possibility of observing pulsar accelerated particles from galactic clusters is considered. 相似文献
11.
We consider the galactic population of gamma-ray pulsars as possible sources of cosmic rays at and just above the “knee” in the observed cosmic ray spectrum at 1015–1016 eV. We suggest that iron nuclei may be accelerated in the outer gaps of pulsars, and then suffer partial photo-disintegration in the non-thermal radiation fields of the outer gaps. As a result, protons, neutrons, and surviving heavier nuclei are injected into the expanding supernova remnant. We compute the spectra of nuclei escaping from supernova remnants into the interstellar medium, taking into account the observed population of radio pulsars.
Our calculations, which include a realistic model for acceleration and propagation of nuclei in pulsar magnetospheres and supernova remnants, predict that heavy nuclei accelerated directly by gamma-ray pulsars could contribute about 20% of the observed cosmic rays in the knee region. Such a contribution of heavy nuclei to the cosmic ray spectrum at the knee can significantly increase the average value of lnA with increasing energy as is suggested by recent observations. 相似文献
12.
The determination of the origin of cosmic rays with observed energies in excess of 1017 eV that exceed the expected energies of cosmic rays accelerated by supernova remnants in the galaxy is a pressing problem in modern astrophysics. Hypernova remnants are one of the possible galactic sources of cosmic rays with energies of up to 1019 eV. Hypernovae constitute a class of extremely powerful supernova explosions, whose supposed progenitors are massive Wolf-Rayet stars. We analyze the special aspects of acceleration of cosmic rays in hypernova remnants that expand in wind bubbles of Wolf-Rayet progenitor stars. We show that these cosmic rays may attain maximum energies of 1018 eV even with a relatively conservative choice of acceleration parameters and account for tens of percent of the total cosmic ray flux observed in the vicinity of the earth in the energy range of 1016–1018 eV if the galactic hypernova explosion rate in the modern epoch reaches ? S ～ 10?4 year?1. 相似文献
13.
A. V. Uryson 《Astronomy Letters》2005,31(11):755-759
We estimate the detection rate of ultra-high-energy cosmic rays on ground-based arrays by assuming that the cosmic-ray sources are active galactic nuclei. We analyze the cases of detection of clusters, several particles that arrived, within the error limits, from the same area of the sky. The adopted model is shown to explain the detection rate of clusters on the AGASA array. 相似文献
14.
D. Harari S. Mollerach E. Roulet 《Monthly notices of the Royal Astronomical Society》2009,394(2):916-922
We analyse in detail the two-dimensional Kolmogorov–Smirnov test as a tool to learn about the distribution of the sources of the ultra-high energy cosmic rays. We confront, in particular, models based on active galactic nuclei observed in X-rays, galaxies observed in H i and isotropic distributions, discussing how this method can be used not only to reject isotropy but also to support or reject specific source models, extending results obtained recently in the literature. 相似文献
15.
In this paper we show that CP-violation is operating in most cosmic-ray sources such as black holes, active galactic nuclei, supernova remnants, and that this leads to the in-equality of the electron—positron component of cosmic rays.Further implications of this result are also discussed. 相似文献
16.
Zhou Da-zhuang
K. K. Tang
《Chinese Astronomy and Astrophysics》1991,15(4):416-422We calculate the spectrum of the diffuse cosmic gamma ray in the single and double leaky box models for several galactic distribution laws of cosmic rays and hdydrogen. The results show that LI Ti-pei's distribution law for the cosmic rays is the best and that the number of interstellar hydrogen molecules should be less than Gordon's value divided by 1.7. The observed spectrum of gamma rays can be reproduced by a suitable choice of the galactic distributions within certain ranges. 相似文献
17.
A simple model of cosmic ray propagation is proposed from which the major experimental results can be derived: The model reproduces
the observed nuclear abundances and accounts for the observed changes of nuclear composition with energy, the high degree
of isotropy of cosmic ray flux at all energies, and the high degree of its constancy throughout the history of the Solar System.
It is consistent with the observed size distribution of extensive airshowers, the intensity and energy distribution of the
electron component, and the diffuse emission of γ-rays and radio waves.
The model is characterized by the two basic assumptions: (1) that cosmic rays have been injected at an unchanging rate by
sources located in the galactic spiral arms and (2) that a large-scale magnetic field retains all particles in our galaxy,
where they interact with interstellar gas, so that all complex nuclei are finally fragmented and their energy dissipated in
meson production and electro-magnetic interactions. 相似文献
18.
We consider the production of high energy neutrinos and cosmic rays in radio-quiet active galactic nuclei (AGN) or in the central regions of radio-loud AGN. We use a model in which acceleration of protons takes place at a shock in an accretion flow onto a supermassive black hole, and follow the cascade that results from interactions of the accelerated protons in the AGN environment. We use our results to estimate the diffuse high energy neutrino intensity and cosmic ray intensity due to AGN. We discuss our results in the context of high energy neutrino telescopes under construction, and measurements of the cosmic ray composition in the region of the “knee” in the energy spectrum at 107 GeV. 相似文献
19.
Micha&#; Ostrowski 《Monthly notices of the Royal Astronomical Society》2000,312(3):579-584
We consider effects on an (ultra)relativistic jet and its ambient medium caused by high-energy cosmic rays accelerated at the jet side boundary. As illustrated by simple models, during the acceleration process a flat cosmic ray distribution can be created, with gyro-radii for the highest particle energies reaching scales comparable to the jet radius or energy density comparable to the pressure of the ambient medium . In the case of efficient radiative losses, a high-energy bump in the spectrum can dominate the cosmic ray pressure. In extreme cases, the cosmic rays are able to push the ambient medium off, providing a 'cosmic ray cocoon' separating the jet from the surrounding medium. The considered cosmic rays provide an additional jet braking force and lead to a number of consequences for the jet structure and its radiative output. In particular, the dynamic and acceleration time-scales involved are in the range observed in variable active galactic nuclei. 相似文献
20.
The role of nearby galactic sources, the supernova remnants, in formation of observed energy spectrum and large-scale anisotropy of high-energy cosmic rays is studied. The list of these sources is made up based on radio, X-ray and gamma-ray catalogues. The distant sources are treated statistically as ensemble of sources with random positions and ages. The source spectra are defined based on the modern theory of cosmic ray acceleration in supernova remnants while the propagation of cosmic rays in the interstellar medium is described in the frameworks of galactic diffusion model. Calculations of dipole component of anisotropy are made to reproduce the experimental procedure of “two-dimensional” anisotropy measurements. The energy dependence of particle escape time in the process of acceleration in supernova remnants and the arm structure of sources defining the significant features of anisotropy are also taken into account. The essential new trait of the model is a decreasing number of core collapse SNRs being able to accelerate cosmic rays up to the given energy, that leads to steeper total cosmic ray source spectrum in comparison with the individual source spectrum. We explained simultaneously the new cosmic ray data on the fine structure of all particle spectrum around the knee and the amplitude and direction of the dipole component of anisotropy in the wide energy range 1 TeV–1 EeV. Suggested assumptions do not look exotic, and they confirm the modern understanding of cosmic ray origin. 相似文献